Blow molding machines for blowing hot parisons made of thermoplastic material to hollow article in blow mold stations located at the periphery of a blowing wheel are known in a wide variety such as for example German reference Nos. 17 04 119, 27 42 693, 23 04 181, 24 54 066 and U.S. Pat. No. 4,036,925. According to this prior art the blowing wheel carrying the blow mold stations as well as the heating wheel for heating the parisons are defined by star wheels having an outer wheel ring which is connected through a plurality of radial arms to a central hub which is rotatably supported around a centercolumn. Details of the bearing means are shown in German No. 24 54 066 for example. The reference shows an upper radial bearing means located in a distance from a lower axial bearing means. The blowing wheel or, respectively heating wheel, is rotatably driven by a tooth gear which is secured to the wheel hub and the tooth gear may be driven from a horizontal shaft through a bevel gear transmission.
In the blow molding art the parisons having a closed bottom are placed on a blow mandrel each, then the blow mandrels are delivered one after the other to the heating wheel, where the parisons pass along stationary heating means. Subsequently, the hot parisons are taken off the heating wheel, may be delivered to an equalizing wheel for equalizing the temperature distribution while they pass around. Finally, the parisons on the blow mandrels are delivered through a further delivery wheel to the blowing wheel and placed in the blow mold stations. Upon closing the blow molds a stretching rod is inserted through the blow mandrel from below into the parison for stretching and blow molding the parison to a hollow article. Thereafter the blow molds are opened and the hollow articles removed from the blow mandrels which are returned to the delivery station for taking up new parisons.
In view of the ever increasing capacity of such blow molding machines, the number of blow mold stations to be mounted on the blowing wheel increased considerably. This results in larger diameters of the blowing wheel and makes improved bearing means necessary to avoid that the blowing wheel exerts wobbling motions around its rotatary axis. This results in problems when the blow mandrels carrying the parisons must be delivered in a very accurate position of height to properly insert the parisons between the blow mold portions. Even a very small axial deviation of the wheel rim from a predetermined height while turning around may lead to difficulties in proper delivering the parisons.